Among the numerous systems known in the state of the art for analyzing the constituents of harvested agricultural products, spectroscopy in the near infrared range (NIR) has prevailed due to various advantages. Compared to an analysis of the constituents using familiar laboratory methods, which may take several hours, NIR spectroscopy provides initial analysis results already within thirty to sixty seconds. Moreover the analyzed samples are not changed or destroyed by the spectrophotometric techniques.
In a typical spectroscopic analysis, samples are exposed to radiation of pre-selected wavelengths and their transmission and/or reflection power is measured. For example filter wheels, diode arrays or diffraction gratings are used to generate the required specific wavelengths.
Due to mobile parts, filter wheels and scanning diffraction gratings are sensitive to vibrations and not reliable when they analyze grain during harvesting. Consequently they are not suited for use on combines or other agricultural harvesting machines, which generate mechanical vibrations.
A device and a method for measuring moisture in harvesting machines is revealed in EP 0 908 087 B1. Here the moisture measuring device is combined with a sensor condition control device in order to forego the otherwise required measuring product-related and processing-related calibrations. Combining the moisture sensor with a sensor condition control device makes it possible to detect erroneous conditions when determining the moisture signal, point them out, initiate corrective action and/or perform a calibration. The sensor condition control device comprises microprocessors as well as suitable evaluation software and can trigger different corrective, display or calibrating measures as a function of the determined measurement status (with plausibility check). For example additional information regarding the crop (e.g. corn, wheat, barley etc.) with corresponding supplemental information (dry, wet, high amount of weeds) can be specified using an input or memory element. This information is taken into consideration in the evaluation of the determined measured values. For this purpose, the moisture sensors arranged in a housing convey the measured moisture values of the conveyed crop. The sensors consist, for example, of an electrode and an electronic system. The suggested solution however only relates to the determination and documentation of the measured moisture values of the crop. No statements can be made about the composition of the crop.
Also the method described in EP 0 960 557 B1 relates to the measurement of crop humidity on a harvester. Here especially the data of a moisture sensor are combined with the data of a mass flow rate sensor and compiled in a map illustrating the deduced moisture content in several areas of the field. The crop's moisture content here is determined by means of its electric conductivity. In this solution as well no statements can be made about the composition of the crop.
Unlike the solutions mentioned above, the documents WO 99/040419 and WO 99/058959 describe arrangements and methods for determining the concentration of the constituents of a sample of harvested agricultural products. The analysis is performed during the harvesting process by means of a spectrometric arrangement in the near infrared range. The constituents of the sample are determined, expressed in a percentage, based on the reflection power of the sample with respect to certain wavelengths. The arrangement for determining the concentration is optically stable and consequently suited for use on agricultural equipment, such as combines. The measurement arrangement comprises a light source for irradiating the crop flow with a plurality of wavelengths, an optical receiver for receiving the reflected radiation, a wavelength separator for separating the received radiation, and a detector for generating intensity signals from the received, reflected and separated radiation. Only the measuring head, which comprises the light source and the receiver, is arranged in the direct vicinity of the measuring crop. The actual evaluation unit with the wavelength separator and detector is arranged, for example, in the cab of the harvester. Fiber optic lines are used to transmit the measured data from the measuring head to the evaluation unit. Since during the analysis of, for example, grain the absorption and reflection behavior fluctuates heavily from one sample to the next, constant calibration of the spectrometer is required. For this purpose a reference standard having a high reflection power, which can be motor-actuated and closes the optical path to the measuring crop for referencing, is arranged in the measuring head. Referencing generally occurs automatically by the control unit. The disadvantage with this solution is that vibrations associated with an operating harvesting machine cause modular interference in the optical fibers or can even damage them. One embodiment of the solution provides for a spatial separation between the measurement arrangement and the evaluation unit comprising a display unit. A connection of the evaluation unit to a harvester, however, is not provided.
WO 99/040419 describes a spectrometer for measuring the constituents of harvested agricultural products, which can be used particularly in combination with combines for real time analysis of grain. The spectrometer used here, which operates in the near infrared range (NIR), allows both chemical and physical properties of different materials to be analyzed. Contrary to ground grain, during the analysis of whole grain, for example, the absorption and reflection behavior fluctuates heavily from one sample to the next. It is necessary to constantly calibrate the spectrometer in order to still achieve accurately measured values. For this, the sample is typically replaced with a standard sample. The spectrometer then provides standard data for calibration of the measurement arrangement. The reflected light is conducted via fiber optic cables to a diffraction grating or an equivalent constituent and is depicted, split by the diffraction grating, on a detector or a detector array. By analyzing the intensity levels of the reflected radiation, the constituents can be determined, expressed in percent. The disadvantage with this solution is that the standard sample is arranged in the measuring head. While this takes various dynamic factors, such as changes in the light source, into consideration, influences arising from dirt on the window of the measuring head cannot be considered and affect the accuracy of the measurement results. Furthermore vibrations can lead to modular interference in the optical fibers or even damage them.
A harvesting machine comprising a sensor operating in the NIR range for measuring the contents and/or properties of crops is described in EP 1 053 671 B1. For the detection of organic constituents preferably wavelengths between 400 nm and 1.7 mm are employed. The sensor, which is arranged outside of an agricultural machine, is appropriately connected detachably to a suitable interface of a data acquisition device so that the properties of the crop picked up by the agricultural machine can be determined and/or crop mapping is possible. The captured measured data can be processed further especially using a computer. Additional sensors allow among other things the crop throughput and the current position (GPS) to be detected and be stored jointly with the measured values relating to the contents or the other parameters with georeferences.
In the still unpublished patent application DE 10 2004 021 448.4 a spectrometric reflection measuring head with internal recalibration is described, where the housing of the measuring head additionally comprises at least two standards, preferably a black and a white standard, for internal recalibration, which can be swiveled optionally in the optical path of the reflection measuring head. After the spectrometer has captured the measured data of both standards, the reflection measuring head is recalibrated by the control and evaluation unit. Additionally, prior to start-up of the measuring arrangement or at certain intervals, at least two external standards can be available for calibration of the reflection measuring head. The measuring head is connected to the spectrometer via fiber-optic lines.
A system for measuring constituents of agricultural products is described in U.S. Pat. No. 6,418,805. The system of this invention comprises a container for holding grain. A movable element is positioned within the container in order to move the grain within the container such that a grain flow is simulated. A probe analyzes the moving grain in real time, while different constituents of the moving grain are determined at the same time from the same grain portion. This detection system for grain samples is suited for the calibration of analysis systems already contained in a device used to process grain or installed thereon at a later time since the rotation of the grain within the container simulates the flow of the grain on a chute or in a line of such a device. A calibration of the device itself is not provided.
US 2002/0039186 A1 describes an arrangement and a method for the spectroscopic analysis of the physical and chemical properties of a sample. The measurement arrangement can be designed as a probe tip in order to be able to take a statistical sample, for example, of a truckload of grain and analyze it. The analysis here occurs while the entire sample is still located on the vehicle or in a container. Based on the properties of this sample, a conclusion is drawn about the properties and constituents of the entire sample. In another embodiment the grain can be analyzed during the unloading process by a measuring head, i.e. while it is in motion. Here nearly the entire sample can be analyzed in real time. For calibration purposes the measuring head comprises an aperture cover, which either allows the light reflected from the measurement object or the reference light to shine on the detector. The reference light is masked off from the optical path of the light source. The aperture cover can also be designed as a reference standard and be brought into a position in which no light shines on the detector in order to capture the dark signal. The existing electronic control system allows the system for the light source to be calibrated automatically. In the arrangement for the spectroscopic analysis, the actual measuring arrangement, which can be designed as a probe tip or measuring head, is connected to the actual control and evaluation unit via electric or fiber-optic lines.
Most systems used to determine the constituents of a sample, however, are designed for laboratory use. Moreover no robust sensors are available on the market that could emit the measured values directly to a bus system. Additionally black/white references are frequently required. The use of fiber optic cables in the measured section prevents the exploitation of a full aperture of the detector and represents a source for errors. The familiar sensors transmit their measured data via cables.